Optics: measuring and testing – By shade or color – Fluid color transmission examination
Patent
1982-11-08
1985-02-19
Evans, F. L.
Optics: measuring and testing
By shade or color
Fluid color transmission examination
250343, 356 51, 356437, G01N 2161
Patent
active
045002070
ABSTRACT:
Apparatus (FIG. 1) for non-dispersive optical determination of the concentration of an identifiable gas, such as a hydrocarbon, in a mixture such as atmospheric air comprises a sample chamber 13 to contain a sample of the mixture, a source 21 of IR radiation at a wavelength absorbed by the gas beamed through the sample chamber to a detector 22 and transducer means to change the gas pressure within the chamber to determine the change in radiation intensity detected at different pressures. One wall of the sample chamber is formed by a flexible diaphragm 25 driven by a voice-coil type transducer 26 whereby the pressure is switched repetitively between the values above and below atmospheric. Atmospheric gas is admitted to the chamber by a porous plug 24 which restricts flow to a low level permitting a pressure change in the chamber. Absorption by the gas relates the intensity of source radiation I.sub.S and measured radiation I.sub.M by I.sub.M oc I.sub.S .multidot.e.sup.-.alpha. o.sup..multidot.g.multidot.p.multidot.x where x is the radiation path length through the sample, .alpha..sub.o is a constant, p the total pressure of the gas mixture and g the concentration of the hydrocarbon gas. By measuring intensity at different pressure involving a change .DELTA.p and a fractional change in intensity of measured radiation .DELTA.I/I, the gas concentration g is determined by applying the relationship:- g=-.DELTA.I/(I.multidot..DELTA.p.multidot..alpha..sub.o .multidot.x).
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patent: 3922551 (1975-11-01), Williams
patent: 4163899 (1979-08-01), Burough
Clarke Dennis P.
Evans F. L.
Ferranti plc
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